1. Field of the Invention
The present invention relates generally to enclosures for handling hazardous materials and, more particularly, to an improved controlled atmosphere work enclosure adapted to be used in dental operatories for mixing, mulling, cutting, and storing amalgam.
2. Discussion of the Prior Art
Of major national concern are health hazards resulting from environmental pollution. Among the more deadly sources of pollution are the heavy metals, and of these mercury is one of the most hazardous and difficult to control.
Of particular concern are the hazards presented through careless handling of mercury in the dental office and dental operatory. In fact, the abnormally high rate of suicide among dentists is believed by many experts to be directly linked to Mercury poisoning. Since the dental profession in the United States uses in excess of 200,000 pounds of mercury per year, or about 4 percent of the total amount used in the United States, a significant threat is presented, not only to the health of the dentist, but to his auxiliary personnel as well.
Environmental contamination through the use of mercury in dental operatories originates primarily from mercury spills and leakage or failure of mercury-containing capsules used in the trituration process. Additionally, mere excitation of any mercury contamination which may reside on the surfaces of the capsules or upon tools and equipment used in the operatory causes the mercury to vaporize and immediately spread throughout the adjacent areas. Also contributing to the inordinately high level of mercury contamination found in dental offices and operatories is simple carelessness by the dentist and his assistants in the open air mulling, amalgam cutting, and mercury storage.
Recent studies show that seven out of ten dental operatories tested showed mercury vapor levels significantly above the threshhold limit of 50 micrograms per cubic meter. These studies further revealed that urinary mercury levels tended to parallel vapor exposure and that the urinary level of the average dentist was twice that of the accepted normal level (20.40 micrograms Hg/24 hrs. vs. 9.95 micrograms Hg/24 hrs.).
One of the detrimental effects of the excessive mercury exposure is acute anxiety. This factor is believed linked with mental illness and it has recently been established through statistical studies that dentists take their own lives twice as often as the general population.
Although mercury contamination poses a particular threat in dental offices and laboratories, the problem is by no means limited to such operatories. Wherever mercury is handled, be it in hospitals, scientific laboratories, or industrial plants, mercury contamination presents a significant health hazard. In hospitals and scientific laboratories, the mercury hazard arises from many sources, including the use of several pieces of apparatus such as the Coulter counter, the Van Slyke apparatus, Miller-Abbot, and Cantor tubes.
In recent years, various approaches have been suggested to control mercury contamination in dental operatories, hospitals, and laboratories. For example, several types of mercury vapor sensing devices have been developed to monitor mercury vapor levels. Similarly, a wide variety of filtered room exhaust units have been proposed to control atmospheric contamination. Little has been done, however, to prevent the contamination from occurring in the first place. Although expedients such as prepackaged amalgam capsule systems, wherein the mercury and alloy are stored and mixed in cartridges, have come into relatively wide use, such systems have exhibited several disadvantages. In addition to the propensity of the cartridges to leak during storage and to break during mixing operations, their handling and disposal after the amalgam is mixed contributes to environmental contamination.
One of the most successful systems developed for use in handling hazardous materials is disclosed in our copending application Ser. No. 672,570. The apparatus of the present invention comprises an improvement of the apparatus disclosed in said application. As will be better understood from the discussion which follows, the work station of the present invention provides a totally enclosed, controlled environment workspace wherein various mercury handling operations such as mixing, mulling, and amalgam cutting, can be accomplished in absolute safety with no fear of personnel or atmospheric contamination. Mercury spills are completely contained within the unit and because of the unique design of the floor of the unit the spilled mercury is collected in a small reservoir or sump from which it can be readily and safely collected, thereby precluding any possible spread of contamination. All mercury handling operations are conducted through rubber gloves which are sealably connected to the unit so as to prevent personnel contamination through direct handling of the mercury. The relative positions of the air inlet and air outlet parts of the apparatus, the novel design of the filters, and the position of the fan unit provide a unique air circulation pattern within the enclosure thereby enabling highly effective control of both vaporous and particulate mercury within the system. In the apparatus of the present invention, unlike that disclosed in our copending application, the air is drawn inwardly through the air inlets, through the work space and then rearwardly and upwardly toward the air outlet. For certain applications this arrangement has proven superior in controlling particulate contamination, particularly when mercury is being handled within the unit. Tests have shown that the mercury level within the air stream emitted from the unit of the present invention during mercury handling operations is consistently less than one half part per million.
The work enclosure of the present invention, when used in the dental operatory, is large enough to accommodate work tables of ample size for loading, mixing, cutting, and storing mercury and mercury alloys. Additionally, the work enclosure is designed to readily accommodate amalgamators of the latest design.
Regular use of the work enclosure of the invention by the dentist and his assistants for all amalgam work virtually eliminates the threat of environmental contamination of the operatory with mercury.
When it is desired to use the work station of the invention in hospitals or scientific laboratories, it is to be appreciated that appropriate internal modifications can readily be made to accommodate numerous types of tools and instruments. Additionally, by use of special filters, the enclosure can readily be adapted to safely handle hazardous materials other than mercury such as toxic chemicals, radioactive materials, and the like.